1. Field of the Invention
The present invention relates generally to a high resolution measuring device, and more particularly to a flexure assembly of a micro scanning device.
2. Discussion of the Related Art
Flexure carriages and devices are known in the art and are used for high resolution instrumentation and measuring equipment such as scanning probe microscopes and the like. These flexure devices typically carry thereon a probe or a sensor, or a specimen to be analyzed. Either the specimen or the probe is moved in very small increments in a plane relative to the other for determining surface or subsurface characteristics of the specimen. These devices are typically designed so as to move highly precisely and accurately in an X-Y plane and yet move very little in a Z direction perpendicular to the X-Y plane. The sensing probe typically measures surface defects, variation of the specimen""s components, surface contour or other surface or subsurface characteristic. These types of devices may also be designed and utilized for other applications as well, such as imaging and measuring properties of computer microchips, computer disc surfaces, and other physical or chemical properties. The range of measurement for such devices is typically on the order of one Angstrom (xc3x85) to several hundred microns (xcexc).
In order to provide this type of extremely high resolution measurement, these devices require precise and minute micro-positioning capabilities within an X-Y plane and yet ideally permit no movement in a Z direction perpendicular to the plane. The flexure devices or carriages which hold the sensing probe or specimen of such devices are designed and utilized to provide just such movement.
A known flexure carriage construction uses a piezoelectric actuator which utilizes an applied electric potential to micro-position portions of the flexure devices. Conventional or known devices typically can only provide very flat movement in an X-Y plane over a very small relative area. The larger the range of movement, the greater the out-of-plane movement becomes, (i.e., the motion becomes increasingly curved or less flat). This is because of the construction and arrangement of the piezoelectric element in the devices. The piezoelectric elements bend partially out of their longitudinal axis and therefore apply out of axis forces which induce errors. The out of axis forces and resultant errors increase with increased expansion of the piezoelectric elements.
One device, disclosed in U.S. Pat. No. 5,360,974 and assigned to International Business Machines Corporation of Armonk, N.Y., provides a fairly flat movement in an X-Y direction or plane utilizing a dual frame arrangement where each frame is supported in opposite directions by flexible legs. Any Z direction motion perpendicular to the plane of one frame of the device is cancelled by movement of the other frame to maintain a very flat movement. However, the disclosed device utilizes long external piezoelectric elements which are oriented parallel to the plane of movement in order to eliminate or reduce rotation or yaw produced by the device. Such a device is much too large in certain applications.
Applications that employ such minute micro-positioning and sensing technology increasingly demand higher resolution measurements. For example, computer technology continues to reduce the size and increase the package density for the electronic elements in microchips and circuits. Meanwhile, the volume in which they are being produced and thus the size of the wafers on which they are made is also increasing. It is therefore becoming increasingly necessary to provide flexure devices which are capable of relatively large ranges of movement in an X-Y plane, which prevent movement in a Z axis perpendicular to the plane, and which are relatively small in size so that they may be utilized in equipment that must be smaller, less expensive and more accurate. It should be understood that while measurement on a smaller scale is being discussed, changes to a sample on similar scales, such as nanolithography and micro-machining, may also need to be performed with this level of accuracy. Thus, the discussion herein is intended to encompass fabrication as well as measurement.
The present invention is therefore directed to an improved flexure carriage and assembly useful in high resolution measurement and fabrication devices and instruments. The flexure carriage of the invention provides extremely flat and true movement in an X-Y direction or plane and prevents movement in a Z direction perpendicular to the X-Y plane. Additionally, the flexure carriage of the invention is capable of producing a relatively large range of motion in both the X and the Y direction while producing such a flat plane of motion. The flexure carriage of the invention produces such advantages and yet may be constructed in a relatively small and very sturdy or stiff package to produce the very flat plane of motion in the X and Y directions.
To accomplish these and other objects, features and advantages of the invention, a flexure assembly or carriage is disclosed. In one embodiment the flexure carriage of the invention is formed of a substantially rigid material and has four elongate columns arranged spaced apart and parallel to one another. Each of the elongate columns has a first and a second end. The carriage also has four first cross members arranged so that each first cross member extends between and interconnects two first ends of the elongate columns. The carriage also has four second cross members arranged so that each second cross member extends between and interconnects two second ends of the elongate columns. The carriage has a translating section that is disposed within a space between the elongate columns generally equadistant between the first and second ends of the elongate columns. The translating section is interconnected to the elongate columns. The carriage has a plurality of flexures wherein one flexure interconnects each first end of each elongate column to each first cross member. One flexure interconnects each second end of each elongate column to each second cross member. At least one flexure interconnects each elongate column with a translating section. The flexures permit the translating section to move according to an applied force in a plane which is essentially perpendicular to the orientation of the elongate columns. The symmetry of the flexure carriage eliminates virtually any movement in a Z direction perpendicular to the X-Y plane.
In one embodiment, a pair of flexures interconnect each elongate column with the translating section. One flexure of each pair is disposed adjacent the translating section on each elongate column nearer the first end. The other flexure of each pair is disposed adjacent the translating section on each elongate column nearer the second end.
In one embodiment, each flexure of the flexure carriage includes a first pair of opposed slots formed transversely and extending toward one another into one of the elongate columns. A first web of the substantially rigid material is left remaining between the first pair of slots. A second pair of opposed slots are spaced from the first pair of slots in the same elongate column and formed transversely and extending toward one another into the elongate column. A second web of the substantially rigid material is left between the second pair of slots. The first web and the second web are arranged perpendicular to one another and spaced apart along the same elongate column.
In one embodiment, a flexure carriage as described above, is provided with a first piezoelectric assembly connected to the translating section for moving the translating section along only a first linear path generally perpendicular to the elongate columns. A second piezoelectric assembly is connected to the translating section for moving the translating section along only a second linear path generally perpendicular to the elongate columns and perpendicular to the first linear path.
In one embodiment, a high resolution measurement device is constructed according to the invention and has a support structure carrying various elements of the device. The measurement device also has a measuring instrument which is carried by the translating section of a flexure carriage provided as described above. Each of the piezoelectric assemblies is affixed at one portion to the support structure of the measurement device and affixed to a portion of the translating section of the flexure carriage for providing applied forces to the translating section for moving the translating section and the measuring instrument therewith.
These and other objects, features and advantages of the present invention will be better understood and appreciated when considered in conjunction with the following detailed description and accompanying drawings. It should be understood however that the following description is given by way of illustration and not of limitation though it describes several preferred embodiments. Many changes and modifications may be made to the disclosed embodiments without departing from the spirit and scope of the present invention and the invention is intended to include all such modifications.